Influence of substrate physicochemical properties and organic matter interactions on phosphorus dynamics in replanted mangrove forests, Southern Vietnam [Elektronische Ressource] / Julian Oxmann

INFLUENCE OF SUBSTRATE PHYSICOCHEMICAL
PROPERTIES AND ORGANIC MATTER
INTERACTIONS ON PHOSPHORUS DYNAMICS
IN REPLANTED MANGROVE FORESTS,
SOUTHERN VIETNAM





Dissertation



For the degree of
Doctor of Natural Sciences

Julian Oxmann














Submitted to the
University of Bremen
Center for Tropical Marine Ecology


2008
























































Erster Gutachter: PD Dr. Rubén José Lara (ZMT, Bremen)
Zweiter Gutachter: Prof. Dr. Otto Schrems (AWI, Bremerhaven)
i
Acknowledgements

I thank PD Dr. Rubén José Lara (ZMT-Bremen, Department of Biogeochemistry,
University of Bremen) for offering excellent conditions in his working group,
supervising my thesis with valuable suggestions and examine the manuscripts.
I wish to acknowledge Dr. Luitgard Schwendenmann (Tropical Silviculture and
Forest Ecology, University of Göttingen) for supporting this work with her insights
in tropical silviculture, for providing AAS data and for reviewing two papers.
Special appreciation is expressed to Prof. Dr. Jeanne Mager Stellman
(Department of Environmental and Occupational Health, Downstate Medical
Center, State University of New York, Brooklyn) for providing military data of spray
missions using a GIS developed by Stellman et al. (2003 a,b), for reviewing a
paper and giving insights into her work of historical range.
I also thank Quinh Huong Pham (Department of Botany and Ecology,
University of Natural Sciences, Ho Chi Minh City) for the productive teamwork in
Viet Nam. She carried out her master thesis during my stay in Viet Nam and
provided assistance in order to acquire official documents. Within the good
laboratory assistance, excellent work has been carried out by Antje & Beate
Bierschenk (Phosphorus Dynamics) and Anneli Strobel (Organic Acids). The
Research Group Crystallography allowed me to do X-ray diffraction of some
synthesised phosphorus specimens at the Department of Geosciences (University
of Bremen). The Terra Mare (Wilhelmshaven, University of Oldenburg) provided
the usage of their laboratories for the preparation of some samples. The
technicians of the ZMT helped with their analytic skills and manpower, particularly
during the first month of the thesis.
I thank the staff of the Department of Botany and Ecology (Saigon) and the
ZMT (Bremen) for the nice working atmosphere, including special thanks to Gaby
Boehme, Ursula Mendoza, Antje Baum, Dorothee Dasbach, Matthias Birkicht,
Dieter Peterke, Anne Baumgart, Dr. Bettina Schmitt, Dr. Aturo Dominici, Dr. Vien
Ngoc Nam and Dr. Tran Triet.
Every involved person can not be acknowledged namely but I remember their
contributions – such as the helpful recommendations of some unknown referees
and the co-operation of the rangers within the Can Gio Mangrove Biosphere
Reserve.
ii
Remark: One should wear adequate clothes within the whole Can Gio
Mangrove Biosphere Reserve, because cobras appear also directly at the low
elevated fringe sites as impressively recognized during the field work.

Finally, I like to acknowledge my mother Renate Oxmann as well as my
brother and scientific co-combatant Dr. Daniel Oxmann for the helpful suggestions
and the interesting topics of conversation.



























iii









Für meinen Vater

Werner Oxmann
25.10.1942 - 27.11.2006




„Die einzige Welt, in der der Mensch ganz er selbst sein kann, ist die Natur.“
Boris Pasternak













iv Contents
CONTENTS

Preface…………………………………....................i – vi

Thesis summary...................................................... 1-4
Zusammenfassung der These................................ 5-9


Thesis introduction............................................. 10-22
Mangrove destruction and reforestation in Viet Nam - Historical relationships . 10
Herbicide spraying and research on herbicide dispersal............................... 10
Mangrove destruction and reforestation........................................................ 12
The structural framework of the manuscripts within the thesis.......................... 18
References ....................................................................................................... 20


Phosphorus dynamics in wetlands – a review . 23-33
Regularly inundated wetlands........................................................................... 23
Rarely inundated wetlands................................................................................ 25
Waterlogged wetlands ...................................................................................... 27
References 29


Quantification of individual phosphorus species in
sediment: A sequential conversion and extraction
method ................................................................. 34-66
Summary .......................................................................................................... 35
Introduction....................................................................................................... 36
Materials and methods ..................................................................................... 39
Sediment sampling and preparation.............................................................. 39
Reference materials for standard addition experiments ................................ 40
Development of the CONVEX method .......................................................... 42
Method evaluation by standard addition experiments ................................... 43
Analytical methods and procedures 44
Results.............................................................................................................. 46
CONVEX method: Soluble phosphate data................................................... 46
CONVEX method: Fractionation data ........................................................... 49
Calculation of the data for P species quantification....................................... 52
Discussion ........................................................................................................ 55
Acknowledgements........................................................................................... 63
References ....................................................................................................... 64


Mangrove reforestation in Vietnam: The effect of
sediment physicochemical properties on nutrient
cycling.................................................................. 67-96
Abstract............................................................................................................. 68
Introduction....................................................................................................... 69
Materials and Methods ..................................................................................... 71
v Contents
Study area..................................................................................................... 71
Station selection............................................................................................ 73
Topography, inundation regime and forest structure..................................... 74
Sampling, field measurements and sample preparation................................ 75
Analytical methods and procedures .............................................................. 76
Results.............................................................................................................. 79
Inundation regime and forest structure.......................................................... 79
Basic sediment properties............................................................................. 79
Sediment pH ................................................................................................. 80
Sediment Eh.................................................................................................. 80
Ca-P and Al/Fe-P: Depth dependency 81
Ca-P and Al/Fe-P: Patterns at particular layers............................................. 82
Available P and leaf P ................................................................................... 84
Sediment N and leaf N ...............................................................................